Intro to Metabolism

Question 1

What happens when glucose levels are low?

Answer 1

The liver can produce glucose and keto bodies

Question 2

Function of insulin?

Answer 2

promote the synthesis of macromolecules

Question 3

Function of glucagon and catecholamines?

Answer 3

break down molecules and provide ATP

Question 4

Function of the AMPK pathway?

Answer 4

Sense low ATP levels and then restore ATP levels

Question 5

What is the mecahnism of the AMPK pathway?

Answer 5

Stimulate catabolic pathways that generate ATP, inhibit anabolic pathways that consume ATP

Question 6

Function of mTOR pathway?

Answer 6

sense amino acid availability, regulate cell growth and cell proliferation, regulate tissue and organ growth
** very important for regulating the cell cycle **

Question 7

Mechanism of mTOR pathway?

Answer 7

stimulate protein synthesis, stimulate ribosomal bigenisis, inhibit autography

Question 8

Function of glucagon

Answer 8

(1) stimulating the liver to break down glycogen to be released into the blood as glucose
(2) activating gluconeogenesis, the conversion of amino acids into glucose
(3) breaking down stored fat (TAGs) into fatty acids for use as fuel by cells

Question 9

Why is C-peptide a good indicator of insulin production?

Answer 9

Because of its longer half life; c-peptide levels are used to differentiate the cause of high insulin in patients

Question 10

Function of insulin

Answer 10

(1) increase glucose uptake
(2) glycogen (glucose polymer) synthesis in the liver and muscle
(3) decrease of glucose in the liver

Question 11

Effects of insulin signaling through receptor tyrosine kinasee

Answer 11

(1) alter protein and enzyme activity (increased GLUT 4 movement to plasma)
(2) dephosphorylation of enzymes (activation of glycogen synthase)
- increase glucose uptake,, glycogen synthesis (in liver)

Question 12

Effect of coffee and tea

Answer 12

Coffee and tea keep activation of glucagon and epinphrine pathways

Question 13

Fate of glucose-6-phosphate?

Answer 13

(1) glycogen synthesis

(2) glycolysis

Question 14

Two signaling pathways of insulin?

Answer 14

(1) ras-dependent signaling (via RAS) -> alterations in gene transcription
(2) ras-independent signaling (via PKB) -> alterations in protein and enzyme activity, dephosphorylation of enzymes

Question 15

Describe glucagon and epinephrine binding to G-protein coupled receptor

Answer 15

activate G-protein -> which activates adenylyl cyclase -> converts ATP to cAMP -> cAMP activates PKA -> PKA phosphorylates protein

Question 16

How are epinephrine and glucagon different?

Answer 16

Epinephrine responds to stress; glucagon responds to low blood sugar; muscle has epinephrine receptors but the liver has receptors for both epinephrine and glucagon

Question 17

Effect of caffeine, theophlline, and other members of the methyxanthine group?

Answer 17

Inhibit phosphodiesterase, leading to increased cellular levels of cAMP

Question 18

What does phosphodiesterase do?

Answer 18

A phosphodiesterase (PDE) is any enzyme that breaks a phosphodiester bond. (found in cAMP)

Question 19

One more time, AMPK pathway - details

Answer 19

(1) stimulated by AMP (AMP comes from ADP after being catalyzed by adenylate kinase)
(2) AMPK promotes catabolism and inhibits ATP consumption
(3) AMPK is inhibited by ATP

Question 20

Role of mTOR and AMPK

Answer 20

act as nutrient and energy sensors and regulate metabolism in conjunction with hormones

Question 21

Intertissue relationships during starvation

Answer 21

Brain: relies on glucose and ketone bodies
Skeletal muscle: relies on uptae ketone bodies and fatty acids, releases amino acids
Liver: uptaes fatty acids, synthesizes and releases glucose and keto bodies
Adipocytes: fatty acids released and used for energy

Question 22

GH

Answer 22

(1) raises blood glucose
(2) anabolic
(3) lipolytic
- stimulates growth primarily through the regulation of the growth promoting hormones IGFs

Question 23

Physiologic targets for AMPK

Answer 23

(1) stimulate GLUT-4 (enhance glucose transport)
(2) stimulate skeletal muscle fatty acid oxidation, glucose uptake
(3) inhibit synthesis of TAGs, glycogen, protein, cholesterol, FAs, insulin
(anabolic processes require ATP)